There are many uses for vessels which may be required to withstand high internal pressures, say up to and even beyond 20,000 p.s.i., whether in the laboratory, industry or the military. One example is a decompression chamber for deep-sea divers, which chamber requires a power source to operate equipment therein, such as rotary gas pumps for circulating the breathing gas mixture through carbon dioxide scrubbers to remove the carbon dioxide. Another example is a high-pressure autoclave used to treat materials at upwards of 10,000 p.s.i. and which may require rotary equipment therein to circulate gases at the high pressures within the autoclave. It is not practical or safe to install electrical motors within such chambers and hence the drive for the rotary equipment for such devices must, perforce, be provided externally of the chambers. It is, of course, necessary to transfer power from a drive motor through the wall of the pressure chamber without permitting the escape of any pressurized gases from the chamber.
Magnetic drives have been used quite satisfactorily in the past to transfer power from a drive motor to rotary equipment within a high pressure chamber. Commonly assigned Canadian Patent Nos. 1,129,469 of Aug. 10, 1982 and 1,146,207 of May 10, 1983 illustrate two examples of prior art magnetic drives which successfully transfer power to high pressure chambers. Both patented devices are intended to keep eddy current losses and heat losses to a minimum during operation, but such devices are somewhat limited by the speeds at which they can operate and the power that they can transmit. They are also somewhat limited, therefore, as to the maximum pressures in which they can operate. The device of U.S. Pat. No. 1,129,469 is limited for example to speeds in the region of 5,000 to 7,000 R.P.M. by its belt drive configuration. There is now a definite need for magnetic drives which can operate at speeds in excess of 10,000 R.P.M. and in pressures of up to, and even beyond 20,000 p.s.i. without generating overly harmful, and wasteful, eddy currents.